On Jun 7, 2013, at 11:34 AM, Camille Teruel wrote:
On 7 juin 2013, at 11:19, Pharo Issue Tracker wrote:
A FogBugz case was edited by Stephane Ducasse.
Case ID: 10840
Title: WeakSet>>#size utterly broken
Status: Resolved (Fix Review Needed)
Category: Bug
Project: Collection
Area: Misc
Priority: 3 - Must Fix
Milestone: Pharo3.0: 30/03/2014
Assigned To: Camille Teruel
URL:
https://pharo.fogbugz.com/f/cases/10840Last message:
Please can you send a mail to the mailing-list so that we all discuss this problems.
Hello everyone,
WeakSet>>#size is broken as demonstrated by the following snippet:
set := WeakSet new.
set add: Object new.
Smalltalk garbageCollect.
set size. "answers 1 instead of 0"
That is because a WeakSet has no mean to know when its items get garbage collected, and thus the tally cannot be updated.
So we need to override #size in Weak, I propose:
size
| counter |
counter := 0.
self do: [ :e | counter := counter + 1 ].
^ counter
But that it rather inefficient for such a simple query.
I would leave size as is, with a comment that by default, it should not be trusted.
Then provide an alternative WeakSet constructor, which returns an instance which registers objects added to it for finalization, with a finalizing action basically doing size := size - 1.
One complication is to make sure to detect and handle the case where object being added is already registered for finalization.
I think the current size-inaccurate should still be the default, as the alternate will (for obvious reasons) sacrifice speed of normal ops for a fast, more* accurate size, and as such should only be used when that is important.
Cheers,
Henry
* In the sense that, I'm not sure what GC actions actually trigger the finalization process� scavenging? Either way higher-than-finalization priority threads can still strictly speaking return inaccurate sizes